Connection Control with B2BUA Located Behind NAT Gateway

Abstract

There is proposed a mechanism for a connection control conducted in a communication network (such as IMS) when a back to back user agent (B2BUA) and network address translation function are involved in the establishment of the connection. When a control network element, such as a P-CSCF, receives a signaling message related to the establishment of the communication connection, via a communication leg coming from a network address translation device, it is determined whether address information contained in an SDP element of the signaling message matches with preset address information allocated to a border gateway function or BGF. When no matching is determined, normal processing like an initiation of a latching procedure at an own BGF is conducted. Otherwise, if a matching address information is determined, i.e. a mirrored SDP is deemed to be present, a latching processing at an own BGF is inhibited and the received BGF's address information are used in the connection establishment procedure. This processing is conducted at all session ends coming from the B2BUA, so that a communication connection with media flow can be established through pinholes of the BGF(s).

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a connection control conducted in a communication network. In particular, the present invention relates to a method, apparatus and computer program product providing a mechanism for connecting two parties in a communication network environment (such as IMS) when a back to back user agent (providing functions like call forwarding etc.) and network address translation function are involved in the establishment of the connection.[0003]2. Related Background Art[0004]Prior art which is related to this technical field can e.g. be found by the technical specification 3GPP ETSI TS 183 017 (current version: 3.2.1) and ITU-T specification H.248.37.[0005]The following meanings for the abbreviations used in this specification apply:[0006]3GPP—3rd generation partnership project[0007]B2BUA—back-to-back user agent[0008]BGF—border gateway function[0009]Call Fwd—call forward[0010]IP—Internet protocol[001...

AI Technical Summary

Benefits of technology

The invention provides an improved connection control mechanism for communication networks, especially in cases where a call processing element and a network address translation function are involved in the connection. This mechanism prevents deadlock situations and avoids the need for extensions in existing signaling protocols. It is particularly useful in private networks with call processing elements such as B2BUAs located behind a NAT or NAPT router. The mechanism allows for successful connection establishment while still utilizing the call forwarding or call transfer functions of the B2BUAs. Overall, this invention provides a more reliable and efficient connection control solution for communication networks.

Problems solved by technology

However, there may be situations where such a processing does not lead to the desired result.

This results in a deadlock situation.

However, the B2BUA is not aware of this deadlock situation.

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